I think we can all agree that Bilbo stumbling into the cave, meeting Gollum, and finding/taking The One Ring is absolutely necessary.

I think we can all also agree that the inclusion of Gandalf the Grey is necessary.

Outside of that, I really don't know what other tie-ins to LoTR are necessary. You have two major characters from LoTR, and you have the single scene that brought about the events of LoTR. Plus, as mentioned in the past, we also have:

A brief cameo by Legolas, while unnecessary, can at least be argued to make sense - given that he is Thranduil's son and could very well have been present in Mirkwood when Bilbo and the Dwarves passed through. So while I'm not a particular fan of it (mostly because I dislike Bloom), it is relatively harmless (so long as it is a brief cameo and nothing more).

I am genuinely curious. What else, in your opinion, is necessary to connect these films to LoTR? I'm not arguing what you said about this matter being subjective. I just honest-to-God can't think of anything else that PJ could think was absolutely crucial - to the point that it HAS to happen.

P.S., your adaptation making more or less money wouldn't make you right or wrong. As that is also a matter of subjectivity .